Method and apparatus for precision blending of composite fluid mediums



Dec. 15, 1964 n. H. HA'rHoRN E'rAL METHOD AND APPARATUS FOR PRECISION BLENDING OF COMPOSITE FLUID MEDIUMS Filed July 6, 1961 INVENTORS. DON H. HATHORN BERNARD T. OLOUGHLIN l $5258 :IIiL

ma IIL United States Patent O M' Okla., a corporation of @eiawsre Filed Iinly 6, 196i, Ser. No. M2939@ 3 Claims, (Qi. 137-8) This invention relates to a method and apparatus for effecting precision blending of a composite iluid medium for flow through a conduit system. ln particular, there is contemplated a method and apparatus which is adapted to proportion ysand and oil for use in the hydraulic fracturing of earth formations.

In treating an oil Well producing formation to increase its productivity, it is a common practice to introduce a fracturing uid into the well and to subject the fluid to high pressure to cause a fracturing and consequent permeability increase in the formation. A particularly elicient fluid medium for this purpose comprises a rened or crude oil in which is interspersed sand which functions as a means to prop or hold open formation fractures formed during the well treating operation.

In performing sand-oil fracturing treatments, the sandoil mixture is conventionally prepared at the well site. At the site, it may be necessary to blend the sand and oil in such quantity `as to enable well injection rates on the order of 40 to 50 barre-ls per minute or" treating rnedium. With such large volume demands, substantial problems are presented in controlling the blending of the sand and oil components so as to consistently and accurately maintain what has been found to be the optimum sand to oil ratio.

In controlling the proportions of medium components, density measuring means may be employed to obtain density measurements of the blended medium which are reflective of the component ratios. ln obtaining such measurements, however, because of operational conditions, it may become necessary to dispose the Cravity measuring apparatus at a position remote from the site of medium component blending. This arrangement is advantageous in that the gravity determining apparatus, thus positioned, efl'ects a measurement of the medium under stabilized flow conditions and at a point in relatively close proximity to the site of medium use. However, because of the remoteness of the gravity measurement from the blending site, there is introduced an undesirable time lag between the time of blending and the time of gravity determination and subsequent proportion correction.

ln addition to the problems involving the placement and timely utilization of the gravity measuring apparatus, there is also involved a substantial abrasion problem in the preparation of the sand-oil mixture. ln blending the oil and sand, considerable agitation is required. However, Where mechanical agitators are employed, they are prone to undergo severe wear as a result of sand induced abrasion.

Recognizing the need for an improved method and apparatus for blending oil and sand constituents, it is an object of this invention to provide a method and apparatus for effecting precision blending of a composite iuid medium having liquid and particulate solid components.

lt is a further object of this invention to provide such an apparatus and method in which the medium component proportions are rapidly corrected when deviations from predetermined proportions occur.

It is an additional object of this invention to provide such a method and apparatus in which the blending of medium components is facilitated by the agitating action il Patented Dec. l5, 1964 ICC of the blended medium itself so as to obviate mechanical wear problems.

To accomplish the foregoing objectives, there is contemplated a method of blending a composite fluid medium for flow through a conduit system wherein a liquid and a relatively heavy, particulate solid component are separately conveyed into the system and there blended to form the medium. Subsequent to this blending, the flow of the medium is accelerated to a rate exceeding the combined rate of component iiow into the system. A portion of the accelerated medium flow is diverted and returned to the blending Zone to agitata the medium components during the blending. The density of the accelerated medium flow is measured; and, in response to this measurement, the flow of the solid component into the system is regulated so as to maintain a consistent medium density. The flow of the liquid component entering the system, which is determinative of the solid component inilow, is regulated to maintain the combined component inow entering the system equal to the medium outflow.

The apparatus for accomplishing the aforenoted blending includes a blending receptacle for receiving medium components, rst conduit means for supplying the liquid component to the receptacle and second conduit means for supplying the solid component to the receptacle. Third conduit means are employed for conveying the blended medium from the receptacle. Rotary pump means are utilized in the third conduit means to accelerate the medium flow to a rate exceeding the combined cornponent flow rate into the system. First branch conduit means extend from the third conduit means to return a proportion of the accelerated medium flow to the receptacle to effect agitation of the medium components. Second branch conduit means also extend from the third conduit means to return another proportion of the accelerated medium iiow to the receptacle. In this second branch conduit means there are included means for measuring the density of the flowing medium. Control means are provided which are responsive to the density measurement of the medium flow through the second branch conduit rreans for regulating the flow of the solid component into the system whereby a consistent medium density is maintained. Means are also provided for measuring the medium level in the receptacle as well as control means which are responsive to the medium level measurement. Such control means regulate the inilow of the liquid component into the system whereby the combined liquid and solid inilow rate is maintained equal to the medium outiiow rate from the system.

ln describing the operational details of the method and apparatus with which this invention is concerned, reference will be made to the accompanying drawing setting forth a schematic representation of the conduit system.

In the self-contained blending system illustrated in the drawing, there is included a liquid material reservoir 1 for storing the oil component of the fracturing fluid and a solid material reservoir 2 for storing the sand component. A mixing tank or receptacle 3 is provided to rece've the liquid and solid components from the liquid reservoir i. and solid reservoir 2.

For conveying the liquid component from the reservoir l to the mixing tank S, conduit means 4 is employed including conduit sections do and db. For the purpose of transferring the solid component from the reservoir 2 to the mixing tank 3, conduit means 5 is utilized which may be arranged to allow gravity induced ilow of the sand. Conduit means d, extending between the mixing tank 3 and a well head 7 of a well to be treated, is also provided, which means includes sections 6a, 6b, 6c and 6d.

A rotary transfer pump S, preferably of the centrifugal type, is installed in conduit means 4 between sections 4a rfrom a predetermined point. Y rferred to the controller 19, is convertedintofanV operating and 4bfor conveying liquid to tank 3. The pump S may be rated ata capacity of 45 barrels per minute, for example. A booster pump 9 is installed in the intermediate portion of conduit means 6, between sections 6a and db for accelerating the outliow of blended medium from the mixing tank. Pump 9, also preferably of the centrifugal type, may be rated at a capacity of 70 barrels per.minute for example. As illustrated,both rotary transfer pump 3 and rotary booster pumpy 9 may be driven-by a common engine 10. Due to their rotary,fcentrifugal character they CTI may be operatedv even during periods of tlow cessation in the system. Adjacent the well head 7, a high pressure injection pump 11 is installed for forcing the treating i fluid carried by conduit means 6 into the Well bore. n

' A branch conduit means 12 extends from conduit section 6b upstream 0f rotary pump 9 black to the mixing tank 3. Where, for example, conduit Vsection db on the' .discharge side of pump 9 is approximately sixrinches in diameter, it is contemplated `that the by-pass 'line 12 would be approximately four inches in diameter.

For controllingfthe density of the blended, .treating uid, a control system is employed including. a density -meter 13, a controller 14,* a `.talvepositioner 15, and a sand valve 16 positioned in conduit means 5 intermediate reservoir 2 and mixing tank 3.

Density meter 13 is installed in a second branch conduit means 17, normally two inches in diameter, which also extends between conduitsection 6b and the mixing` "tions 5b and 6c, allows the medium supplyto be disconregulated to equal the medium'outflow rate, i.e. the rate at which medium is injected into'a well. -The rate of solid material inflow being a function of the blended medium density, this .inflow is proportional toand vdetermined by Y Vtherilow of liquid material enteringfthe system. By contank 3. While a varietyof conventional meters may be i employed, it isrpreferredthat a density meter be utilized such as that shown in the Composite Catalog of Oil FieldV Equipment land Services, .1960-61 edition, page v2360.

This density meter is of the type which generates apneu.

matic signal proportional to the density of the fluid medium passing through the conduit in vwhichfit is installed. This pneumatic signal is transmitted to the air supplied controller 14 which in turn transmits an operating signal determined by positioner 15, regulatesthe rate of sand ow through the conduit 5 required to'maintain the desired medium density. f Y

Pneumatically operated controller Maud valve posisolid material through conduit 5 to maintain a proper density level is dependent upon the outflow'load condi-v material consequence. ponentV feed arrangement may be obtained by allowing Y tive jet lfeed, arrangement.

trolling the liquidv inflow to maintain a constant level'of components in mixing tank 3, it is insured that the combined rate of liquid `and solid inflow is equal to the outilow of blendedmedium.

In controlling the system, it is important to insure the availability of v,at least a minimum-supply of the medium components. -For purposes of systemstability, the available supply rates should be consistent. Accordingly,rin meeting theA high liquid demand, the use of transfer pump d in supplying this component in' a positive fashion is'of While ya satisfactory solid comsand to ilow by' gravity through conduit VSrinto mixing tank 3, there maybe alternatively'employedA a more posi- Y Y Vfrom reservoir'Z and passed through valve V16 would ow v into a hopper and there into the path of a iluid jet. This jet would impel the sand axially through conduit means into the mixing tank 3. By supplying oil as the jet'iluid, thereimay be obtained a premixing of the sand and oil Y :components prior toV their entry intoy the vmixing tank 3.

Ato the valve positioner 15. The position' of valve 16, yas

' .tioner 1.5, both being conventional structures in the con- ,I trol art are not illustrated. However, as the. inflowrof tion, it is preferred that the controller 14'be of:V the pro-l j portional and reset type,ethe operating characteristics of which .are described in the article .Basic Controller f Fundamentals appearing at page V54 in the September 1960, issue of Automation Magazine. v

The regulation of the combined inflow solid components of Vthe medium is eiected by a control system including a pressure or liquid level measuring celly v18 positioned in the mixing tank 3, air supplied controller 19, a valve positioner 20, and an oil valve 21 positioned -in conduit section 4b between the rotary pump 8 and the mixing tank 3. The cell 1d, controller 19, and valvepositioner 20,'beingconventionaland Well known apparatus are shown only in schematic form.v The cell 18 is designed to issue a` pneumatic signal proportional tothe or liquid ma The sand feeding jet may be suppliedfrom transfer pump 8 or 'alternatively by the booster pump 9.

By Virtue of the use of the blended medium accelerating, Ybooster pump Y9, a'particularly eiicient density control and blending action isachieved in the' system. The

`use of the by-pass conduits 12 and 17 enables the con. stantcirculatiomof a material quantity of blended medi-` um through a closed circuit comprising conduit portions 6a, pump 9, conduit portion 6b, parallel branch conduits 12 and 17, and mixing tank 3. This closedcircuit within the system enables the rotary pump ,9 to bevoperated constantly and independent of system oultlow at a'relatively high ratetofeiect an acceleration of the `:llow of .the blended mediumto ka rate whichk is materially greater than the combined liquid and solid componentowrate entering thev system. Thefaccelerated lirow in this circuit deviation of the medium level `withinvthe mixing tank Thisjsignal, when transsignal which, through means `of theV valve positioner Ztl, determines theA position of valve 21v necessary to cause the oil inliow rate necessary to maintain Vthe predeterminedf facilitates the obtaining of uniformV and completesuspen-y sionofA the particulate, i.e.,'V sand,llcomponent.^ In thus insuring the forming of `a homogeneous suspension ror slurry,rthe accuracy of the/density meter signalasf'measured in the circuit is enhanced.v 'In addition, and of con-y siderable importancefthe time' lag isgreatly reduced be- `tweertthe-time of 'medium Iblending 'and the time of obtaining a measure of medium density at a'point of Stabi# tions may be effected. v

fAn additional advantage'in .accelerating the medium flow involves the obtainingof `thegrelatively,high speed lizeclV tlow, suchthattimelyV corrections of density devia- .flow in relatively highca'pacity branch conduit 12. This rapid-.and material flow; when returnedto the mixing levelwilth'in'th'e tank 3. As the levelcondition 'to be'co-n` trolled is not variable, the controllerv mayl be ofthe prportional type disclosed inthe article Basic Controller YFundamentals?appearing at Vpage 54 'infthe September' 1960,*issue'v oflutomation Magazine. l

In addition to the automatic tlow controlling valves in y j the system, manual valves suchas valvesZZ, 23, and 24 fare provided. Valve 22, positioned between conduit sec.

tank`,in and of itself, issutlicientt0'l produce an agitating or blending actionrof 'the vcomponents entering YtheY tank such that mechanicallblending devicesarey not required.

VWhile the method land,apparatusof this invention have Y been described inconnection'pwith their utilization' in the' blending of a sand andoil V'slurry for use inwell fractur- 5` ing operations, `itis readily apparentthat theirapplicability is notr limited;with respect "to the componentsv of a ln this scheme, sand issuing enoteca slurry being blended nor w 1 respect to the irtended function of the blended slur Clearly, :for example, the liquid components mig t lm water, gelled water, a light hydrocaroon, etc. Simile. ,1, solid components other than sand might be utilized, ot which components cement is only example. iepartures from the preferred and described. embodiment of the invention will readily occur to those skilled in the art which are well within the scope of the invention as defined in the appended claims.

We claim:

l. A method ol @fleeting precision blending of a composite tluid medium for llow through a conduit system, said method comprising: conveying a liquid component of said medium into said sy ern, conveying a relatively heavy, particulate, solid component of said medium into sm'd system, blending said liquid and solid components to form said composite medium, applying pump pressure to said thusformed medium so as to accelerate its flow to a rate exceeding the combined liquid and solid component ilow rate into the system, diverting a first portion of said accelerated medium' ilow and using said iirst portion to agitato said liquid and solid components during said lending, with the rate of ilow of said rst portion being selectively variable, diverting a separate, second portion of satid accelerated medium flow, independent of said rst portion, and mixing said second portion with said solid and liquid components during blending, measuring the density of the medium tlow in said second diverted portion after the acceleration thereof, and at a point within said system where said medium ilow is continuously subject to pump pressure and in continuous motion, regulating the ilow of said solid component entering said system in response to the thus measured density of said medium to maintain a consistent medium density, and regulating the dow of said liquid component entering said system to maintain the combined liquid and solid component inllow rate equal to the medium outilow rate from the system.

2. An apparatus for effecting precision blending of a composite fluid medium for flow through a conduit system, said apparatus comprising: a blending receptacle for receiving medium components, iirst conduit means for supplying a liquid component of said medium to said receptacle, second conduit means for supplying a relatively heavy, particulate solid component of said medium to said receptacle, third conduit means for conveying said blended medium from said receptacle, iirst rotary pump means for conveying said liquid component through said first conduit means, second rotary pump means for accelerating the medium flow in said third conduit means to a rate exceeding the combined liquid and solid component flow rate into the system, rst branch conduit means extending from said third conduit means to return a portion of said accelerated medium flow to said receptacle to agitate said liquid and solid components during said blending, second branch conduit means extending from said third conduit means to return a portion of said accelerated medium flow to said receptacle, means for measuring the density of medium flowing through said second branch conduit means, irst Valve means in said second conduit means for regulating the inflow of said solid component, control means kresponsive to the density measurement of said .medium flow through said second branch conduit means for regulating the position of said rst valve means to thereby regulate the inflow of said solid.. component through said second conduit means whereby a consistent medium density is maintained, means for measuring the medium level in said receptacle, second valve means in said rst conduit means for regulating the inflow of said liquid component,l control means responsive to the medium level measurement in said receptacle for regulating the position of said second valve means whereby the combined liquid and solid component inflow rate is maintained equal to said medium outflow rate from the system, and valve means in said rst branch conduit means for selectively varying the flow therethrough, said third conduit means and second branch conduit means being continuously subject to pump pressure applied by said second rotary pump means whereby the ilow of said medium through said second branch conduit means is continuously subject to pump pressure and is in continuous motion, with said flow through said second branch conduit means being independent of the ow through said first' branch conduit means.

3. An apparatus for effecting precision blending of a composite iluid medium for iiow through a conduit syste i, said apparatus comprising: a blending receptacle for receiving medium components, first conduit means for supplying a liquid component of said medium to said receptacle, second conduit means for supplying a relatively heavy, particulate solid component of said medium to said receptacle, third conduit means for conveying said lended medium from said receptacle, first rotary pump means for conveying said liquid component through said first conduit means, second rotary pump means for accelerating the medium ow in said third conduit means to a rate exceeding the combined liquid and solid component tlow rate into the system, irst branch conduit means extending from said third conduit means to return a portion of said accelerated medium flow to said receptacle to agitato said liquid and solid components during said blending, second branch conduit means extending from said third conduit means to return a portion of said accelerated medium ilow to said receptacle, means for measuring the density of medium flowing through said second branch conduit means, control means responsive to the density measurement of said medium flow through said second branch conduit means for regulating the inflow of said solid component through said second conduit means whereby a consistent medium density is maintained, means for measuring the medium level in said receptacle, control means responsive to the medium level measurement in said receptacle for regulating the inlow of said liquid component through said rst conduit means whereby the combined liquid and solid component iniow rate is maintained equal to said medium outiiow rate from the system, and Valve means in said first branch conduit means for selectively varying the flow there'rn'ough, said third conduit means and second branch conduit means being continuously subject to pump pressure applied by said second rotary pump means whereby the ilow of said medium through said second branch conduit means is continuously subject to pump pressure and is in continuous motion, with said ow through said branch conduit means being independent of theV flow through said rst branch conduit means.

References @lated in the file of this patent UNYED SmATES PATENTS oupun oct. '17, 1961 

1. A METHOD OF EFFECTING PRECISION LENDING OF A COMPOSITE FLUID MEDIUM FOR FLOW THROUGH A CONDUIT SYSTEM, SAID METHOD COMPRISING: CONVEYING A LIQUID COMPONENT OF SAID MEDIUM INTO SAID SYSTEM, CONVEYING A RELATIVELY HEAVY, PARTICULATE, SOLID COMPONENT OF SAID MEDIUM INTO SAID SYSTEM, BLENDING SAID LIQUID AND SOLID COMPONENTS TO FORM SAID COMPOSITE MEDIUM, APPLYING PUMP PRESSURE TO SAID THUS-FORMED MEDIUM SO AS TO ACCELERATE ITS FLOW TO A RATE EXCEEDING THE COMBINED LIQUID AND SOLID COMPONENT FLOW RATE INTO THE SYSTEM, DIVERTING A FIRST PORTION OF SAID ACCELERATED MEDIUM FLOW AND USING SAID FIRST PORTION TO AGITATE SAID LIQUID AND SOLID COMPONENTS DURING SAID BLENDING, WITH THE RATE OF FLOW OF SAID FIRST PORTION BEING SELECTIVELY VARIABLE, DIVERTING A SEPARATE, SECOND PORTION OF SAID ACCELERATED MEDIUM FLOW, INDEPENDENT OF SAID FIRST PORTION, AND MIXING SAID SECOND PORTION WITH SAID SOLID AND LIQUID COMPONENTS DURING BLENDING, MEASURING THE DENSITY OF THE MEDIUM FLOW IN SAID SECOND DIVERTED PORTION AFTER THE ACCELERATION THEREOF, AND AT A POINT WITHIN SAID 